The host of the railing. 
   Namespace:   Autodesk.Revit.DB.Architecture  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 22.0.0.0 (22.1.0.0) 
  Since:  2013 
Syntax
Remarks
 If the host will be a Stairs in  MultistoryStairs  element, use  [M:Autodesk.Revit.DB.Architecture.Railing.SetMultistoryStairsPlacementLevels(System.Collections.Generic.ISet`1{Autodesk.Revit.DB.ElementId})]  to set the base levels of the stairs where the railing should be placed. 
 If %hostId% is the id of a Stairs Component (Run or Landing), it means that the Railing will be hosted by the Stairs element but railing adjustment to the stairs will start from the Component. If a stairs id is set as a host, the lowest stairs component below or above the railing sketch will be chosen as the host instead.
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | When setting this property: The hostId is not a valid railing host. | 
| Autodesk.Revit.Exceptions ArgumentNullException | When setting this property: A non-optional argument was null |